The present invention relates to a locking device for the drive shaft of a rotating tool member of a working tool, especially a cutting tool of a trimmer etc., wherein a securing element is fixedly connected to the drive shaft and has a catch opening for a locking bolt. The locking bolt is axially displaceably supported within the housing of the working tool and cooperates with an actuating element that displaces the locking bolt from its locking position within the catch opening into a release position outside of the catch opening. The locking bolt is axially displaceable by a cam which projects into the travel path of the locking bolt and which is actuated by the actuating element.
From German Patent Application 195 42 144 a reliable locking device is known in which the locking bolt is permanently loaded by a spring force in the direction of the locking position at the securing disc. The cam projecting into the travel path of the locking bolt is connected to a turn knob and can release the locking bolt counter to the force of the spring into a release position. The turn knob must be secured in its position in which it holds the locking bolt in the release position to counteract the spring force of the spring acting on the locking bolt is supported and, on the other hand, to compensate acceleration forces resulting from operation of the cutting tool and acting on the locking bolt.
It is therefore an object of the present invention to improve a locking device of the aforementioned kind such that the acceleration forces acting on the locking bolt in its release position can be securely compensated to thereby prevent the accidental actuation of the locking device.